PowerBook - Recovery

I have searched the forums before putting this problem to light.
Today i turned on my powerbook, all my settings throughout have returned to how you would a a mac when you first take it out the box and set it up.
All my cookies are lost, all programs are acting as if i am using them for the first time etc.
I wanted to know is there anywhere i can go to restore the computer to an earlier state, i know this feature appeared in windows. ALl i know is i had a problem with trying to delete skype from my machine, and did delete a file to do with that late last night, and then deleted the trash folder, the computer remained as normal, but today i turned it on, and it is reset.
IF anyone knows about what could cause this problem, or how i can prevent it happening again, i would be most grateful, i have not really lost anything major, but all the settings, and my many internet bookmarks and preferences are all gone...
Any help would be very much apprecaited.
Regards
Jameslerouge

I think this is probably a really simple problem to rectify for someone who knows. I was messing around the slidebar last night too, and i think i may have changed the name of my account, basically all the information and i want is now in a new folder, and when i now log in to my mac, it seems to treat me as a new user, even though i have made no new accounts. Does anyone know anything that could have somehow caused my mac to now behave as if i am a new user, i have lost all my settings and templates, and it is driving me mad.

i now realise using a google search rather than the search on here, this matter has been covered many times. I do believe i may well have changed my user name, and now attempting to follow steps given have now managed to revert my settings again, so todays progress has now been reset.
Basically i am not sure what the original name was for my account on the slide bar, and i am now so confused i just want to reset it back to how it was, and i know this is a very simple thing for someone who knows, if anyone can give an explanation for dummies, i would be most grateful. I have had this machine for over 3 years, god knows why i decided to change a name last night, and why oh why is it so simple to do, and then causes a day of misery?